The invention relates to a method and an apparatus for generating control signals for, in particular, the control of the fuel quantity delivered to an internal combustion engine. Other variables subject to the control signals may be the ignition angle and the exhaust gas recycle rate.
Known in the art are methods for determining the duration of fuel injection control pulses which are based on the storage of a set of engine characteristics which are read out for each operational state of the engine as recognized by appropriate sensor signals. The set of characteristic data may be a family of curves relating the throttle valve position to the engine speed (rpm). An open loop control of this type cannot react, however, to deviations and changes of the characteristics that were first set when the engine was new and which are due to aging and wear and tear. For example, various elements and transducers may be subject to drifts, or the engine itself may undergo changes, so that the originally programmed set of characteristic data is no longer correct. Therefore, the fuel metered out to the engine will not be such as to optimize the exhaust gas composition and will therefore not permit the engine to comply with exhaust gas restrictions. The non-optimal performance may also lead to increased fuel consumption and undesirable changes in the operation of the engine.
It is also known to superimpose, on the forward, open loop control based on a characteristic set of data, a closed loop control which uses the output signal from a so-called oxygen or .lambda.-sensor located in the exhaust gas and corrects the fuel quantity fed to the engine so as to maintain a desired engine operation. It is also possible to detect the engine roughness and use that signal as a controlled variable for closing the mixture control loop. These systems however are subject to the following considerations. An internal combustion engine is subject to very rapid changes in operational state and thus requires a rapidly acting closed loop control. This rapid response is counteracted and impeded by the relatively large delays which are due to the time which must pass between the induction of air into the engine and the exhaust of the combusted mixture which provides the control signal.